Final Velocity

In gunnery, is the technical term for the uniform velocity which a projectile would acquire in falling through an indefinite height in the air. A body falling in vacuo is uniformly accelerated, its velocity being continually increased. In the atmosphere the case is different. Since the resistance of the air increases with some power of the velocity greater than the square, it follows that at some point in the descent the retardation becomes equal to the acceleration, and the body will move with uniform velocity. This is called “final velocity,” and is one of the most important elements in the theory of projectiles. Every projectile has its own “final velocity.” Other things being equal, that projectile is best which has the greatest “final velocity.” The “final velocity” of a given projectile will depend upon its weight on the one hand, and the extent of surface and the way it is presented to the air on the other. The extent and form of the surface directly opposed to the action of the air will largely determine the resistance. The best form, as determined by the experiments of Borda, is the ogival . The resistance, other things being the same, may be taken as proportional to the area of greatest cro -section. The weight in spherical projectiles is proportional to the cube of this dimension. It follows from these general principles that large projectiles are better than small, dense better than light, solid better than hollow, in regard to their final velocities; moreover, that oblong projectiles are better than spherical, ogival-headed oblong better than flat-headed, and long rifle projectiles better than short, in the same regard.